1. Field of the Invention
The present invention relates to a torque converter including a converter housing, a turbine wheel rotatably arranged for rotation about a converter axis of rotation relative to the converter housing, and a bridge coupling for the substantially rotation-proof selective coupling of the turbine wheel to the converter housing. The bridge coupling comprises a coupling mechanism connected in substantially rotation-proof fashion to the turbine wheel and having at least one friction surface which can be selectively brought to rest on a counter friction surface provided on the converter housing or selectively connected thereto in rotation-proof fashion.
2. Description of the Related Art
A prior art torque converter of this type is known, for example, from DE 34 10 526 A1. In this prior art torque converter, a coupling disk may be brought to rest with its substantially flat and substantially radially-extending friction surfaces on a counter friction surface of the converter housing for establishing the bridging state. In this known torque converter, the following problem exists. During operation, due to the high working fluid pressure prevailing in the interior of the converter housing and also due to centrifugal forces, the converter housing becomes distended, especially in the radially outer area. As a result, the counter friction surface provided on the converter housing is positioned at a slant relative to the friction surface in this condition. The consequence of this is that the essential contact between the friction surface and the counter friction surface is moved radially outward, and what is known as edge carrying or edge friction is produced. This produces disproportionate wear on the friction surface or the counter friction surface in the radially outer area and thus considerably impairs the useful life of the torque converter. The disproportionate wear causes an overload or "burning" of the coupling in the radially outer area where the friction occurs.
In the torque converter known from the prior art, the problem also exists that a coupling piston, which generally carries the friction surface in its radially outer area, is, like the converter housing, deformed by the pressure prevailing in the converter interior. Specifically, the deformation is such that the coupling piston is pressed in its radially inner area toward an axial end side of the converter housing. This causes the coupling piston being pivoted or deformed around a circumferential line region. When the coupling piston undergoes a pivoting movement, the friction surface connected thereto pivots as well, so that a slanted position of the friction surface relative to the counter friction surface is again created. The aforementioned deformation of the coupling piston causes an especially disproportional load occurs in the radially inner area of the friction surface or the counter friction surface.